time to
make the fuel hot enough to burn, as it does above, where it is carried in
small quantities into the wick, and has all the effect of the heat
exercised upon it.

There is another condition which you must learn as regards the candle,
without which you would not be able fully to understand the philosophy of
it, and that is the vaporous condition of the fuel. In order that you may
understand that, let me shew you a very pretty, but very common-place
experiment. If you blow a candle out cleverly, you will see the vapour
rise from it. You have, I know, often smelt the vapour of a blown-out
candle--and a very bad smell it is; but if you blow it out cleverly, you
will be able to see pretty well the vapour into which this solid matter is
transformed. I will blow out one of these candles in such a way as not to
disturb the air around it, by the continuing action of my breath; and now,
if I hold a lighted taper two or three inches from the wick, you will
observe a train of fire going through the air till it reaches the candle.
I am obliged to be quick and ready, because, if I allow the vapour time to
cool, it becomes condensed into a liquid or solid, or the stream of
combustible matter gets disturbed.

Now, as to the shape or form of the flame. It concerns us much to know
about the condition which the matter of the candle finally assumes at the
top of the wick--where you have such beauty and brightness as nothing but
combustion or flame can produce.

[Illustration: Fig. 2.]

You have the glittering beauty of gold and silver, and the still higher
lustre of jewels, like the ruby and diamond; but none of these rival the
brilliancy and beauty of flame. What diamond can shine like flame? It owes
its lustre at night-time to the very flame shining upon it. The flame
shines in darkness, but the light which the diamond has is as nothing
until the flame shine upon it, when it is brilliant again. The candle
alone shines by itself, and for itself, or for those who have arranged the
materials. Now, let us look a little at the form of the flame as you see
it under the glass shade. It is steady and equal; and its general form is
that which is represented in the diagram, varying with atmospheric
disturbances, and also varying according to the size of the candle. It is
a bright oblong--brighter at the top than towards the bottom--with the
wick in the middle, and besides the wick in the middle, certain darker
parts towards the bottom, where the ignition is not so perfect as in the
part above.

[Illustration: Fig. 3.]

I have a drawing here, sketched many years ago by Hooker, when he made his
investigations. It is the drawing of the flame of a lamp, but it will
apply to the flame of a candle. The cup of the candle is the vessel or
lamp, the melted spermaceti is the oil, and the wick is common to both.
Upon that he sets this little flame, and then he represents what is
true--a certain quantity of matter rising about it which you do not see,
and which, if you have not been here before, or are not familiar with the
subject, you will not know of. He has here represented the parts of the
surrounding atmosphere that are very essential to the flame, and that are
always present with it. There is a current formed, which draws the flame
out--for the flame which you see is really drawn out by the current, and
drawn upward to a great height--just as Hooker has here shewn you by that
prolongation of the current in the diagram. You may see this by taking a
lighted candle, and putting it in the sun so as to get its shadow thrown
on a piece of paper. How remarkable it is that that thing which is light
enough to produce shadows of other objects, can be made to throw its own
shadow on a piece of white paper or card, so that you can actually see
streaming round the flame something which is not part of the flame, but is
ascending and drawing the flame upwards. Now, I am going to imitate the
sunlight, by